Valdivian temperate forests
climate zone of central Chile, represent a veritable biogeographic island, separated from climatically similar areas by the extensive Pacific Ocean barriers and flanking deserts. Rainfall varies so dramatically within the ecoregion, that some of the sub-units can be considered dry forests, with others classified as rainforest.The Valdivian temperate forests and the more hygrophilous vegetation of the mediterranean
The Valdivian temperate forest is characterised by its extraordinary endemism (e.g., 90 percent at the species level and 34 percent at the genus level for woody species) and the great antiquity of its biogeographic relationships. However, faunal species richness is only modest, with only 290 vertebrate taxa having been recorded, in spite of the broad latitude niche available.
Its taxons show close philogenetic relationships dating to the early Tertiary, with Gondwanic taxons of Oceania forming more recent relationships with Neotropical taxons, separated from other biotas in South America by the great mountainous barrier of the Andes. The region's ecosystems are frequently threatened and degraded. Urgent action has been recommended to restore the ecoregion's ecology and to preserve its remaining natural habitats.
Location and general depiction
This ecoregion is located in the southern cone of South America. It covers a rather narrow continental strip between the western slope of the Andes and the Pacific Ocean, running from approximately 35° to 48° south latitude.
The tree-line elevation occurs at around 2400 metres (m) in central Chile (35°S), descending to 1000 m in the south of the Valdivian region. The Andean mountains at these latitudes rise above 3000 m. At these higher elevations the temperate forests disappear and are replaced by high Andean vegetation. Maximum annual average temperatures vary between 21°C and 13°C in the northern and southern ends of the ecoregion, respectively. Minimum annual average temperatures range from 7°C to 4°C. The most pronounced variations in average temperatures occur from west to east, due to an increase in altitude toward the Andes. This change in temperature often occurs in less than 160 km of longitude, with more moderate temperatures on the coast and more extreme temperatures in the Andes. Annual precipitation varies between 1000 mm in the north and more than 6000 mm per year in the southern part of the ecoregion. Rain-fronts correspond chiefly to the belt of westerly winds arriving from the Pacific Ocean, with their activity concentrated on the Chilean slope of the Andes, where high mountains create a rain-shadow effect on the eastern versant. Precipitation decreases significantly on the eastern slope of the Andes in Argentina, where rainfall of less than 200 mm is recorded only 100 km east of the Andean peaks. These rains are seasonal due to the Mediterranean-like climate with concentrated rains in the winter months. This seasonality declines from north to south.
Three major geological circumstances define this ecoregion:
- The Andes range, with heights above 3000 m and frequent volcanic and seismic activity, has been the center of glaciation processes which transformed the biota of the temperate forest during the Pleistocene (previous two million years).
- The coastal range is a mountainous belt approximately 100 km to the west of and parallel to the Andes. This range is from the Jurassic age, formed on a metamorphic rocky basement from the Paleozoic age. It has moderate heights at a maximum of 1300 m, breaking off toward the south of the Chiloé Archipelago (43.5°S).
- The intermediate depression or central valley is a lower fault zone (100 to 200 m) covered by volcanic ash and glacial morainic fields lying between the two ranges. The soils of both ranges are poorly developed because the Andean slopes are young and the coastal range is severely weathered. The soils of the intermediate depression have been formed by sedimentary deposits from both mountain ranges.
The temperate forests of southern South America have been isolated from other continental forest biomes since the mid-Tertiary. The connection with other forest ecosystems in South America was probably broken by the end of the Tertiary, and has remained so during the entire Quaternary. Phytogeographic analyses of the Tertiary fossil record in Chile show that about 60 percent of the tropical genera in Chilean forests during the early Tertiary disappeared from the territory during the latter half of the Tertiary. These extinctions were due to a remarkable contraction of the tropical vegetation belts in the Southern Hemisphere that transpired in the mid to late Tertiary.
In the Quaternary, a succession of climate change cooling and warming cycles produced massive mountain glaciers that advanced during the cool glacial periods, causing repeated contractions of the geographic range of temperate forests on the western edge of southern South America. These processes were followed by expansions of the forest during briefer and warmer interglacial periods. Immigration of species from tropical latitudes was no longer possible due to the extreme aridity established in the subtropical latitudes on the western edge of South America, and the Andean mountain barrier to the east. The increased aridity, reduction in area, and isolation of temperate forests led to the extinction of many congeneric plant species, resulting in the presently high number of monotypic genera in the austral forest flora.
Climate change during those prehistoric times combined with geographic isolation resulted in a net loss of species, particularly taxons with tropical ancestry. At the time when glaciers reached their maximum extension in the southern hemisphere, species-rich rainforests survived near the northern limit of their present distribution. Rainfall in this northern area was probably higher during the glacial period and temperatures were moderate due to oceanic influences. Some areas in the coastal range between 38°S and 40°S including specific places in Argentine Patagonia could have remained free of ice and periglacial processes that restricted the persistence of vegetation in the proximity of glaciers. These plant communities may have represented the sources for the recovery of regional biodiversity following deglaciation.
Biogeographic events, temperature and precipitation gradients, the long history of isolation and recent great climatic changes have produced a heterogeneous mosaic of forest types in the ecoregion. The forest ecosystems from north to south were based primarily on a classification proposed by Gajardo and the scheme of Veblen. There are five types of forest ecosystems:
- Deciduous forests of Maule Province (Chile) representing the transition between Mediterranean-type schlerophyllous forests and wet temperate forests further south. These forests are characterized by the dominance of deciduous species of Nothofagus, with many of these species endemic to this area.
- Valdivian laurel-leaved forests dominated by a variety of tree species, including Tepa (Laureliopsis philippiana), Tique (Aextoxicon punctatum), Ulmo (Eucryphia cordifolia), Caldcluvia paniculata, and Weinmannia trichosperma.
- Northern Patagonian forests with a predominance of evergreen species such as Coigue (Nothofagus dombeyi), Chilean Podocarp (Podocarpus nubigena) and Winter's Bark (Drimys winteri).
- Patagonian Andean forests, include Monkey Puzzle Tree (Araucaria araucana) and other taxa of high Andean scrublands with deciduous Nothofagus, which are widely distributed latitudinally.
- Evergreen forests and bogs consist of evergreen forests of Guindo Beech (Nothofagus betuloides) and bogs of Sphagnum spp.
The Valdivian temperate forests ecoregion can be subdivided based on criteria of vegetation and woody formations, leading to eleven distinct units or sub-ecoregions. Three of these cover both east and west versants of the coastal range, and two are basically found in the intermediate depression. These five units or sub-ecoregions are found only in Chile. Six sub-ecoregions are confined to the Andean slopes, one of them entirely in Argentina (xeric cyprus forests), and the remaining five are shared by Chile and Argentina.
There is an unusually high diversity of plant families represented in South American temperate forests (nearly 50% of the plant families in the Chilean flora are found in temperate forests), which contrasts with the lower species richness (only 7.8 percent of the flora of Chile). The main biological value of the southern temperate forests resides in their high endemism. A high number of taxonomically isolated genera belong to monogeneric families including Aextoxicaceae, Gomotergaceae, Desfontaineaceae, Eucryphiaceae, and Misodendraceae. The high percentage of endemic species, close to 90% of the seed plants, suggests geological antiquity, long isolation, and high rates of extinction during the cooler Pleistocene. The entire ecoregion contains 700 to 800 species of vascular plants, representing more than 200 genera. Of the 32 genera of trees exclusive to the Valdivian forest, twenty-six (81%) are monotypic. At least one-third of the woody plants are of Gondwanic origin, with their closest relatives being found in Australia, New Zealand, New Caledonia, and Tasmania.
For the temperate forests of southern South America, endemism at the species level is estimated to be 50% for vines, 53% for hemiparasites, 45% for all vertebrates, 76% for amphibians, 50% for freshwater fish, 36% for reptiles, 33% for mammals, and 30% for birds. A number of special status taxa are found in the ecoregion, such as Near Threatened Species (NT), Vulnerable Species (VU), Endangered Species (EN), Critically Endangered Species (CR).
Faunal species known to be extinct in this ecoregion are two crustacean species within the genus Aegla and some species of the family Tenebrionidae (Coleoptera). Both groups of invertebrates previously inhabited woody habitats of the coastal range, one of the most critically endangered sub-ecosystems in the ecoregion.
There is a highly diverse set of anuran species Many of the amphibians in these forests have very narrow distribution ranges, particularly in the coastal range. Amphibians limited to the Nahuelbuta Range at 38°S include Bullock's False Toad (Telmatobufo bullocki CR), an endemic anuran to the Valdivian temperate forests. Also limited to the Nahuelbuta Range and endemic to the Valdivian temperate forests are Vanzolini's Spiny-chested Frog (Alsodes vanzolinii CR), Cabreria Spiny-chest Frog (Alsodes barrioi VU), and Contulmo Toad (Eupsophus contulmoensis VU). Other species found further south in the coastal range with narrow distributions ranges include: the ecoregion endemic Barrio's Frog (Insuetophrynus acarpicus CR), the ecoregion endemic (Eusophus vertebralis NT) and Pelado Mountains False Toad (Telmatobufo australis NT).
The Chile Darwin's Frog (Rhinoderma rufum CR); Rosy Ground Frog (Eupsophus roseus NT); Mocha Island Ground Frog (Eupsophus insularis CR); Miguel's Toad (Batrachyla antartandica EN); Olive Spiny-chest Frog (Alsodes verrucosus); Red-spotted Frog (Rhinella rubropunctata); Nibaldo's Wood Frog (Batrachyla nibaldoi); Nahuelbuta Ground Frog (Eupsophus nahuelbutensis); Alsodes australis, Batrachyla fitzroya, and Malleco Spiny-chest Frog (Alsodes vittatus) are also anurans endemic to the Valdivian temperate forests; moreover, the Chile False Frog (Telmatobufo venustus CR) is endemic to the ecoregion and found only on the Chilean western versant of the Andes. The Challhuaco Frog (Atelognathus nitoi VU) has only been collected in a very narrow environment on the Andean slope at the edge of the ecoregion. Another non-threatened endemic is the Emilio's Ground Frog (Eupsophus emiliopugini).
Special status but non-endemic anurans are: Darwin's Frog (Rhinoderma darwinii VU); Portozuelo Frog (Atelognathus salai VU); Chilean Giant Frog (Calyptocephalella gayi VU). Achala's Four-eyed Frog (Pleurodema kriegi NT), a taxon chiefly known to the Cordoba Province of Argentina, but catalogued by WWF as occurring in the Valdivian region.
Other non-endemic, non-threatened anurans found in the Valdivian temperate forests are: Banded Wood Frog (Batrachyla taeniata); Chile Four-eyed Frog (Pleurodema thaul); Tonchek Spiny-chest Frog (Alsodes gargola); Chiloe Island Ground Frog (Eupsophus calcaratus); Emerald Forest Frog (Nannophryne variegata); Concepcion Toad (Rhinella arunco); Patagonian Toad (Nannophryne variegata); Gray Wood Frog (Batrachyla leptopus); Island Spiny-chest Frog (Alsodes monticola); Marbled Wood Frog (Batrachyla antartandica); Warty Toad (Rhinella spinulosa); and the Yellow Cururu Toad (Rhinella icterica).
There are a number of reptilian taxa present in the Valdivian temperate forests, especially within the Tree Iguana group; example ecoregion endemics here are: the Curicen Tree Iguana (Liolaemus curicensis) and the Cyan Tree Iguana (Liolaemus cyanogaster).
Not only are there forest birds present in the ecoregion, but there are terrestrial avian species such as the Lesser Rhea (Pterocnemia pennata). The Slender-billed Conure (Enicognathus leptorhynchus) is endemic to the Valdivian temperate forests, and whose range extends from Chiloe Island to the heights of Mount Aconcagua.
Endemic mammal species are also biologically interesting because of their kinship to geographically remote groups. This is the case with Dromiciops gliroides, an arboreal marsupial found in this ecoregion, located in the basal trunk of Australasian and American marsupials. Another Valdivian temperate forests ecoregion endemic is the Chilean Climbing Mouse (Irenomys tarsalis). An endangered herbivore found in the ecoregion is the Chilean Guemal (Hippocamelus bisulcus). The Chilean Shrew Opossum (Hippocamelus bisulcus NT) is another Valdivian temperate forests endemic.
In general, the southern temperate forests are characterized by flora with one of the highest incidences of pollination and dissemination by animals recorded in any temperate biome, particularly in comparison with the northern hemisphere. In temperate forests of southern South America, the flowers of about 85 percent of woody plant genera are visited and presumably pollinated by animals. This ecoregion has extremely singular bees, in which many important neotropical subfamilies like Meliponinae and Euglosinae are entirely absent, but characterised by the presence of endemic and possibly relict groups such as Xeromelissinae, Diphaglosa, Cadeguala, Corynura, Neofidelia, Manuelia, and Eucerinoda.
Around one fifth of the woody plant genera produce red tubular flowers that are visited by Sephanoides sephaniodes, the only species of hummingbird that lives in these forests. About 50% to 70% of the woody plant species or genera produce fleshy fruits; these percentages indicate the importance of the seed dissemination by fruit-eating vertebrates.
Upon the arrival of the Spaniards, most of the area defined as the Valvidian ecoregion was effectively covered by forests with few open areas being cultivated by indigenous Mapuche groups. Currently, the forest cover has declined by one-third of the estimated area at the arrival the Spanish colonists, with a current area of about 12,600,000 hectares. The remaining forested area corresponds to an area (about one half) of secondary forests. There are few remaining primary forests, especially in the coastal range. If the current rates of deforestation outside the areas of protection continue, the forest will disappear within the next 20 years.
The National Parks in the temperate forests of Chile and Argentina are considered pioneer protected areas in Latin America. Some of these Parks were established in the early 1900s. There are more than fifty parks, reserves and monuments protecting more than 10 million hectares in the temperate region of Chile. There is a great disparity between the distribution of these protected areas and the geographic distribution of trees and vertebrate species. The lowest percentage of protected areas (less than ten percent) is found in the areas with the highest biodiversity in Chile, between 35.6° and 41.3°S. Most of the protected areas within these latitudes contain the greatest wealth of species found above 600 m, where physical processes that produce impoverished speciation and endemism are accentuated. In addition, the areas with the greatest wealth of species are found precisely in areas with high human density, and thus there is great pressure from agriculture and plantation forestry. The protected areas in the Andes of Chile and Argentina represent 99% of the total surface area protected in the southern part of South America, in contrast to protected areas in the coastal range at the same latitude. The Andean forests are more impressive than the coastal forests, due to vistas of imposing volcanoes, great lakes, and small mountain lagoons, based on the prevailing landscape criteria used when creating Andean parks. There are no protected areas in the intermediate depression, with the exception of a small municipal park near Puerto Montt.
Types and severity of threats
The main threats to the Valdivian temperate forest include logging for commercial purposes and firewood. Agriculture is replacing the species-rich native forests with monocrops of exotic species. Areas are deforested for kindling large road works such as the southern coastal highway and the bridge over the Chacao Channel that will link the continent and the Island of Chiloé. Deforestation in the foothills of the Andes and in the coastal range has been one the most massive and rapid in Latin America prior to 1980. About 15,000 to 49,000 hectares of natural vegetation were burned each year between 1970 and 1990. Reptile exports intensified and the number of reptile specimens exported grew from 3548 to 60,000 between 1985 and 1992. Approximately 24,064 specimens of amphibians were exported between 1985 and 1992. In Argentina, the main threats are pressure from tourism, replacement and invasion by alien species, the impact of the European deer, and the introduction of freshwater fish.
Justification of ecoregion delineation
The forests of Valdivia represent the a unique assemblage of ancient species, both floral and faunal, which today persist as relicts of Gondwanaland. This ecoregion is also host to many endemic species. The forests are bound to the north by one of the most arid deserts on the continent (Atacama), traverse the southern Andes and are bound on the east by grasslands, and to the west by the Pacific Ocean. The southern delineation marks the gradual change in tree species composition to a Nothofagus-dominated forest, which are termed the Megallanic subpolar forests. The initial linework for these southern temperate rainforests follow a variety of sources and have undergone a number of modifications to reach this final polygon. Expert opinion during several ecoregion priority setting workshops (Valdivia, Chile [April 19-21, 1999], Bariloche, Argentina [October 19 & 20, 1999], and Concepción, Chile [March 24, 2000]) resulted in Chilean winter-rainforests being lumped in with Valdivian forests, and the western linework was extended further into Argentina to encompass the historic range.
- For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.
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